A conventional solenoid driven pneumatic valve may be used to control a fluid flow. When electrically energized or de-energized, a solenoid driven pneumatic valve may cut off and/or permit one or more fluid flows. An actuator of a solenoid driven pneumatic valve is an electromagnet. When the valve is energized, a magnetic field builds up to pull and/or push a plunger against the action of a spring. When de-energized, the plunger returns to its original position by action of the spring. Solenoid driven pneumatic valves are discussed, by way of example, in the reference “Technical Principles Of Valves” (omega.com, One Omega Drive, Stamford, Conn., 06907, J-3 to J-7), the disclosure of which is hereby incorporated herein in its entirety by reference.
A flow of air (or other fluid) through a valve may be a function of a number of controlled port connections and a number of switching positions. Directional valve functionalities may be described by referring to them as a combination of “ways” and “positions”, such as, for example, a 4-way 2-position valve also referred to as a 4/2-way valve. The term “way” defines a number of controlled flow paths the valve has (indicated by arrows in ISO symbology). With respect to the term “position”, a pneumatic directional valve may have two or three switching positions (indicated by squares in ISO symbology).
In a conventional 5-way, 2-position solenoid driven pneumatic valve (a 5/2 valve), fluid flows may be controlled between first and second actuator ports, first and second exhaust ports, and an air supply port. When the solenoid is energized, the 5/2 valve may provide fluid coupling between the air supply port and the first actuator port, and between the second actuator port and the second exhaust port. When the solenoid is de-energized, the 5/2 valve may provide fluid coupling between the air supply port and the second actuator port, and between the first actuator port and the first exhaust port. A 5/2 valve may thus be used to control operation of a pneumatic actuator coupled to the actuator ports.
A solenoid driven pneumatic valve, however, may be subject to mechanical wear that may reduce a useful life thereof. In addition, functionalities provided by a solenoid driven pneumatic valve may be limited. Moreover, a solenoid driven pneumatic valve may be unable to maintain an energized position in the event of a loss of power.